That does not, in my experience, look like it was inflicted by another quail. I think the others are right, and a motion camera or wireless webcam might be a really good idea. These types of quail attract a lot of predators. Even if it seems like nothing can get in, an adult rat can squeeze into any space large enough for its skull to fit through, and a mouse can get into a 1cm by 1cm hole.
In addition to a camera, you might want to put some rat traps outside and around your enclosure. I have had one rat kill over 30 budgies in a single night just for fun, so it's better to be safe than sorry.